The United Nations has imposed an embargo on arms shipments to Ivory Coast since 2004 amid fighting between the government and rebels in the northern part of the country. The two sides signed a peace agreement in 2007, but there have been repeated cease-fire violations, said prosecutors who outlined the charges against Yao.

An informant told federal agents in San Jose more than a year ago that a U.S. resident, Michael Shor, was trying to broker the shipment of 4,000 handguns, 200,000 rounds of ammunition and 50,000 tear gas grenades to Ivory Coast, an agent said in a court affidavit. It did not say which side was to receive the weapons.

This was a "major weapons-smuggling scheme," said John Morton, director of the customs agency.

Shor was arrested in April after one or more conspirators wired $1.9 million to a San Jose bank account, controlled by the government, as a 50 percent down payment on the weapons, the affidavit said. It said Shor's cooperation led agents to Yao, who was shown a sampling of the weapons at a warehouse in August and made plans to conceal their shipment to Africa. He was arrested after the remaining $1.9 million was wired to the bank, prosecutors said.